Chair base



FIG. 1 is a top perspective view of a chair having a base _according to the invention, the seat portion thereof being _shown in phantom;

FIG. 2 is a side elevation view thereof;

FIG. 3 is a front elevation view thereof;

FIG. 4 is a rear elevation view thereof; and

FIG. 5 is a top sectional view of the base taken along the plane of line 5--5 in FIG. 3. 

The ornamental design for a chair base, as shown and described. 